1. Field of the Invention
This invention relates to balloon catheters, commonly used to drain a body cavity such as the bladder. In particular, this invention relates to novel designs of balloon catheter that enable it to overcome several major disadvantages and deficiencies in the prior art.
2. Description of Prior Art
Since the Foley type balloon catheter was invented in 1965, it has become the most widely used catheter in urology. Many patients require the assistance of such catheters for a myriad of reasons including incontinence, bladder outlet obstruction (such as from prostatic hypertrophy, stone or tumor), urethral stricture, trauma and post-surgical recovery. There are two major types of balloon catheters, the most common being the "two-way" Foley which has 2 channels and is used primarily for drainage, and the "three-way" Foley which has 3 channels and is used for irrigation and drainage. Both types of catheters have drainage openings situated distal to/above the balloon, just proximal to the catheter tip.
The most important function served by balloon catheters is the drainage of urine from the bladder. When the natural passage of urine from the bladder is impaired for whatever reason, the patient is at risk of developing a spectrum of complications including bladder and kidney infections, secondary septicemia, renal failure and even death.
Unfortunately, three factors associated with bladder catheterization further predispose the already compromised patient to such infections: First, the very act of catheterization risks introduction of pathogens into the urinary tract. Second, the incomplete drainage of the bladder resulting from using currently available catheters which have drainage openings situated above the balloon, encourages stagnation and promotes bacterial growth. And third, pressure against the bladder mucosa exerted by the catheter tip (causing "polyposis cysta/bladder callus/catheter tip necrosis"), or by negative pressure in the drainage tubing (causing hemorrhagic pseudopolyps), all lead to weakened local defenses against bacterial invasion and colonization. Millions of elderly and debilitated patients, including those suffering from progressive or traumatic neurologic disorders such as multiple sclerosis and paraplegia also chronically depend on indwelling catheters for bladder drainage. In addition to the aforementioned problems which can manifest even after a few days of catheter therapy, these patients are at high risk of developing bladder infections and bladder stone formation from chronic incomplete drainage of urine from the bladder. Because currently available catheters do not drain from the lowest portion of the bladder, renal casts, concretions and sediments settle and accumulate in the bladder neck leading to painful stone formation tha usually require surgical removal.
Even for short term use, the irritation caused by the catheter tip often leads to pain and bladder spasms. The protruding tip of the catheter is also a concern to the surgeon after bladder surgery since it may disrupt suture lines. Lastly, the histologic changes in the bladder mucosa induced by pressure from the catheter tip, or suction injury from negative pressure in the drainage tubing, can confuse diagnosis upon cystoscopy in that the inflamed area may need to be biopsied in order to rule out malignancy. The problems and complications described in the preceding paragraphs result in patient discomfort, morbidity and mortality that cost millions of dollars in added health care costs annually.
There is considerable prior art attempting to improve the design of the basic balloon catheter to overcome the aforementioned problems. Ericson in U.S. Pat. No. 3,438,375 (April 1969) disclosed several embodiments of catheters, the balloons of which either do not fully buffer the bladder mucosa from the catheter tips or when they do, come with blunt catheter tips that are difficult to insert. By nature of their shared inferior design, the Ericson catheters also have much narrower lumens which predispose them to early obstruction and failure.
Morton in U.S. Pat. No. 3,811,448 (May. 1974) disclosed a catheter with a conventional tip and drainage opening distal to an asymmetric one-sided balloon which when inflated will cause the catheter tip to bend and lower the distal opening, thus marginally improving bladder drainage. In addition, just below the lower border of the balloon is another drainage opening. This opening is situated too low to be consistently within bladder cavity to serve drainage function.
Hutchison in U.S. Pat. No. 3,954,110 (May. 1976) disclosed a "bilobated" balloon enclosing a reinforced catheter tip, said balloon is retracted inferiorly at two diametrically opposite points to expose two drainage openings. The balloon is designed to give early indication of the correct positioning of the catheter within the bladder and also intended to drain the bladder completely. However, the fully circumscribing balloon above the drainage openings in combination with the funnel-shaped bladder neck make it likely that as the bladder empties, its wall will collapse around the greatest transverse diameter of the balloon, shutting off the body of urine from the drainage openings and thus impede further drainage. The design of the blunt reinforced catheter tip also renders the catheter difficult to insert.
Stevens in U.S. Pat. No. 4,022,216 (May 1977) disclosed a balloon catheter that has its tip enclosed by a second, more distal balloon. The extra balloon increases the cost of manufacture and upon inflation, adds to the total length of the catheter in the bladder, limiting the degree of free collapse of the bladder and can indirectly cause the very type of pressure injury it was designed to avoid. Since the Stevens catheter has a conventional type drainage opening that is above the retention balloon it also cannot allow for complete drainage of the bladder.
Kasper et al. in U.S. Pat. No. 4,284,081 (August 1981) disclosed a doughnut shaped balloon mounted transversely at the distal end of a catheter, said balloon has a funnel-shaped drainage opening. While this design may allow slightly better, but still incomplete, drainage of the bladder, it creates a serious problem in the process. The outflaring distal orifice and the transversely positioned balloon make insertion difficult, requiring the use of a stylet which increases risk of trauma. Furthermore, the critical relationship between the radial boss on the stylet and the annular boss on the catheter is such that the catheter lumen must be considerably and disadvantageously narrowed by the annular boss in order to attain any reasonable degree of protection against accidental perforation of viscus by the stylet.
Wiita et al. in U.S. Pat. No. 4,351,342 (September, 1982) disclosed several embodiments of balloon catheters, the tips of each is completely encased by, and free floating (except for one three-way catheter embodiment) in, said balloon upon inflation. This free-floating tip design cannot ensure that the catheter tip will be buffered by the balloon, for the following reason: Tilting, angulating or thrusting of the catheter as can happen with any patient movement, may lead to catheter tip pushing right against the relatively untethered balloon wall, thus abrogating the very benefit such design is supposed to provide. Because the drainage opening in each of Wiita's catheter embodiments ends above the inferior border of its corresponding retention balloon, complete bladder drainage cannot be achieved by either his two-way or three-way designs. Also since each drainage opening is completely and circumscribingly surrounded by a balloon, not only would the catheter's manufacture be complicated by a high incidence of balloon failures, in clinical use, the contracting bladder wall during emptying will close upon this type of drainage orifice easier and sooner, leading to obstruction and incomplete emptying.
More recently, Nordqvist et al of Sweden disclosed in U.S. Pat. No. 4,575,371 (March 1986) a catheter with a unique tulip-shaped balloon which when inflated, projects distally to surround the tip of the catheter, much like flower petals shielding the pistil. The intended goal is to prevent the catheter tip from impinging against the bladder mucosa and to prevent negative-pressure suction injuries. The unusual balloon design, calling for a thicker wall proximally and angling against the direction of insertion would make both manufacture and its insertion difficult. The narrow funnel-shaped crevice between the catheter tip and the inflated balloon also promote sediment collection and encrustation leading to early obstruction. The Nordqvist balloon catheter also does not permit complete drainage of the bladder.
None of the aforediscussed prior art since Foley has enjoyed any commercial success, presumably due to the inherent drawbacks in their design. It is apparent from the preceding review of prior art, that a still unmet need exists for a balloon catheter that is simple and economical to manufacture, easy and comfortable to insert, prevents catheter tip irritation and mucosal suction injury, consistently and reliably achieve complete bladder drainage and allow for efficient and thorough irrigation. It is the object of the present invention to provide a novel, unique catheter possessing all of the above desirable characteristics.